Generally it is known that in systems which are able to perform oscillations, the stiffness and the damping of a connection that allows oscillations can be computed when the oscillation excitation and the oscillation response are known.
In the field of soil compaction, this possibility is used to compute, from known parameters of the compaction machine and from parameters of the oscillation excitation of the unbalance type vibrator of the machine and of the oscillation response of the contact body (roller or bottom plate) of the machine, which are determined during compaction operation, the soil stiffness, and thereby be in position to draw conclusions with regard to the degree of compaction of the soil.
However, due to the unidirectional linking between the soil and the contact body of the compacting machine there arises the problem that, depending on the soil stiffness and the mode of operation of the compacting machine, three different operating conditions can occur.
In a first condition, which is also termed “contact operation”, during acting upon the soil with the contact body there exists at any time a contact between the contact body and the soil.
In a second condition, which is also termed “periodical loss of contact”, during acting upon the soil with the contact body it occurs in uniform intervals a contact loss between the contact body and the soil.
In a third condition, which is also termed “jumping”, during acting upon the soil with the contact body it occurs in unsteady intervals a contact loss between the contact body and the soil.
The three before described operation conditions can generally occur in all systems which are able to perform oscillations and are having an unidirectional linking.